The present invention relates to a method for manufacturing a decorative molded article that has a decorative design surface.
One method for manufacturing a decorative molded article is an in-mold decoration method (for example, refer to Japanese Laid-Open Patent Publication No. 2013-146956). In this method, a mold having a cavity block and a core block and a plastic sheet are used. The plastic sheet has a base sheet and a decorative design layer formed on the base sheet. The plastic sheet will hereafter be referred to as a film.
When manufacturing a decorative molded article using this method, the film is positioned relative to and secured to the cavity block in the opened mold. The film is then caused to closely contact the inner surface of the molding cavity (a molding surface) of the cavity die by vacuum suction. Thereafter, the body of an article body is molded by injecting molten plastic into a cavity, which is defined between the film and the core surface of the core block while the mold is clamped. In the molding process of the article body, the decorative design layer of the film is transferred (adhered) to the design surface of the article body. As a result, the obtained decorative molded article includes a decorative design layer decorating the design surface of the article body.
In the manufacturing method disclosed in Japanese Laid-Open Patent Publication No. 2013-146956, the film secured to the cavity block is pushed prior to the vacuum suction, so that the film is deformed to have a shape close to the molding surface of the cavity die. Thus, compared to a case in which a film is subjected to vacuum suction without being deformed in advance, the amount of movement of parts of the film is reduced in the vacuum suction. This limits positional displacement between the molding surface the cavity block and the decorative design layer when the vacuum suction is applied. As a result, the obtained decorative molded article includes a decorative design on the design surface formed with great positional accuracy.
In the above described manufacturing method, to properly change the shape of the film through vacuum suction, the film is caused to closely contact the opening periphery of the molding recess of the cavity block prior to the vacuum suction. This seals the space defined by the molding surface of the cavity block and the film. Thus, if, in this state, the film is pushed to cause the film to approach the molding surface of the cavity block, parts of the film that are not pushed bulge, and the film is deformed into an unintended shape. Such an unintended deformation of the film causes positional displacement of the film (the decorative design layer) relative to the molding surface of the cavity block. This degrades the accuracy of the positions of the design on the design surface of the decorative molded article.
Such drawbacks are not limited to the above described method for manufacturing a decorative molded article by the in-mold decoration, but are generally common to methods for molding at least a part of a decorative molded article by vacuum suction using a plastic sheet such as a film. For example, the drawbacks are found in a method for manufacturing a decorative molded article with a decorative design surface by a film insert molding or vacuum molding.